This invention relates to a papermaker's fabric, and more particularly, to a papermaker's press felt with a woven three-layered base fabric construction.
The most common technique for removing water from a paper sheet is by the use of a press wherein the paper sheet and the felt on which it is carried are squeezed between rollers, the felt being formed in such a manner that the water extracted from the paper will press through the felt for discharge. Desirably, the press felt will have relatively large open areas or voids which will enhance the water-containing capability and serve to avoid a backflow of water relative to the direction of motion of the paper web, with consequent "crushing" or hydraulic destruction of the structural integrity of the web.
Various felts have been designed with the objective of providing void space. These felts, though, have other problems as a result of their structure. For example, in a press felt which contains a relatively coarse, incompressible woven base fabric to provide void volume, the very incompressibility of the yarn comprising the base fabric, acting as intermittent backing elements to the associated fibrous batt layer, tends to produce regions of varying pressure as the fabric passes through the press nip. Since a smaller portion of the surface area of the paper is effectively exposed to pressure being exerted upon it than if the fibrous layer were more uniformly supported underneath by the base fabric, the felt is less effective as a water removal device and surface marks are sometimes introduced in the paper.
Accordingly, it is an object of this invention to provide a papermaker's felt that will avoid "crushing" of the web by providing void volume through the nip between press rolls.
It is a further object of this invention to provide a papermaker's felt in which the pressure exerted by the felt on the paper is uniform, without localized hard spots which are likely to produce marks in the paper.
It is still a further object of this invention to provide a papermaker's felt having an enhanced capacity for removing water from a paper sheet.